The invention relates to a fuel filter assembly for use on motor vehicles and the like and more particularly to a fuel filter assembly having a conductive feature which facilitates draining off to ground the electrical charge generated by passage of fuel through the filter assembly.
For many years, fuel filters in motor vehicles comprised a filter element disposed within a metallic housing at a convenient location in the fuel line, often times in the engine compartment of the vehicle. While hoses to and from the housing were generally rubber and thus non-conductive, the housing was secured to a metal component or panel of the automobile and thus grounded. Accordingly, any electrostatic charge generated by passage of the fuel through the filtration element was readily and safely grounded through the filter housing to the motor vehicle body.
The constant examination of vehicle weight directed to weight reduction as well as continuing development of plastics and polymers has affected the fuel delivery and filtration systems of vehicles as it has most other vehicle systems. Rather than metal, filter housings are now frequently fabricated of a fuel tolerant plastic such as nylon. Such a construction results in a filtration element being isolated from the vehicle ground. An electrostatic discharge (ESD) may result as the charge in the filtration element increases and seeks ground. Frequently, such discharge occurs through the housing to the most proximate metallic vehicle body feature. Repeated discharge can result in leakage through the filter housing which is unacceptable.
In response to this problem, filtration devices have been developed which seek to eliminate electrostatic discharges and their consequences by providing a path to ground which prevents build up of an electrostatic charge. For example, U.S. Pat. No. 5,382,351 teaches plating the housing, inside and out, with a conductive material such as chromium, nickel or copper by vacuum metalization or sputtering.
United U.S. Pat. No. 5,898,560 discloses a filter having a conductive housing with an electrically conductive member and means for converting laminar flow to turbulent flow.
U.S. Pat. No. 4,999,108 teaches a fuel filtration device having a perforated metal cylinder with inner and outer filter elements. The cylinder is in contact with a wire in an end plate which communicates with a conductive mounting stud.
The foregoing are but three of many United States Patents directed to the above-referenced difficulty and it is therefore apparent that fuel filtration devices directed to minimizing or eliminating the problem of electrostatic discharge are highly desirable.
A fuel filter assembly adapted for disposition in a housing includes an inner filtration element, an outer conductive surround and end caps which position and secure the filtration element and conductive surround. The filtration element preferably includes an outer layer of depth filtration media and an inner pleated paper element. The conductive surround is preferably conductive extruded plastic mesh. The end caps may be formed of a fuel tolerant plastic such as nylon or acetal. The filtration element may be disposed in a housing having suitable inlet and outlet fittings and a conductive path for achieving electrical conductivity from the exterior of the housing to the conductive surround for facilitating draining off of an electrical charge. In a preferred embodiment, the end caps are conductive plastic. In a first alternate embodiment, the end caps are non-conductive and the conductive mesh extends beyond the end caps. In a second alternate embodiment, an additional outer layer of depth filtration media disposed on the exterior of the preferred or first alternate embodiment filter assembly.
It is thus an object of the present invention to provide a fuel filter assembly intended to minimize electrostatic discharge.
It is a further object of the present invention to provide a fuel filter assembly having an inner filtration element and an outer conductive element.
It is a still further object of the present invention to provide a fuel filter assembly having a pleated paper filter surrounded by a depth media filtration layer.
It is a still further object of the present invention to provide a fuel filter assembly having a conductive, extruded mesh surround which cooperates with adjacent conductive elements to drain off electrostatic charge from fuel passing therethrough.
It is a still further object of the present invention to provide a fuel filter assembly and housing wherein a conductive mesh surround defines an electrical connection with the exterior of the housing to drain off electrostatic charges created by fuel filtration.
Further objects and advantages of the present invention will become apparent by reference to the following description of the preferred embodiment and appended drawings wherein like reference numbers refer to the same component, element or feature.